knock down vs lay low

knock down

verb
  • To hit or knock (something or someone), intentionally or accidentally, so that it falls. 

  • To drink fast. 

  • To disassemble for shipment. 

  • To reduce the price of. 

  • To demolish. 

  • To approve a drinking toast by banging glasses on the table. 

  • At an auction, to declare (something) sold with a blow from the gavel. 

lay low

verb
  • To topple or overcome; to cause to fall; (of a person) to knock out. 

  • simple past tense of lie low 

  • To lie low, to be inconspicuous, especially when the potential object of search. 

How often have the words knock down and lay low occurred in a corpus of books? (source: Google Ngram Viewer )